The present invention is generally related to light sources, and more particularly to traffic signal lights including those incorporating both incandescent and solid state light sources.
Traffic signal lights have been around for years and are used to efficiently control traffic through intersections.- While traffic signals have been around for years, improvements continue to be made in the areas of traffic signal light control algorithms, traffic volume detection, and emergency vehicle detection.
One of the current needs with respect to traffic signal lights is the ability to generate a homogenous light beam, that is, a light beam having a uniform intensity there across. Conventional incandescent lights tend to generate a light beam having a greater intensity at the center portion than the outer portions of the light beam. With respect to current solid state light sources, while LED arrays are now starting to be implemented, the light output of these devices can have non uniform beam intensities, due to optics and when one or more LEDs have failed.
A particular problem with current traffic signal lights is that the cover for the housing retaining the light source is comprised of two pieces, a lens piece and a lens holding member. The interface between the lens and the lens holding member is typically sealed with a rubber seal to retard water and environmental elements from communicating with the light source and enclosed electronics. However, time, temperature and extreme operating conditions quickly degrade this environmental seal, which degradation limits the operation and operational life of the signal head. Since conventional detachable lenses are prone to allowing environmental elements to penetrate this light housing, the DOT personnel are often required to go up in a bucket truck to clean the signal including both the inner surface and the outer surface of the lenses.
Conventional traffic signals are also typically equipped with external video cameras and sensors for monitoring traffic. These electronic devices are being disposed external to the traffic signal which exposes these devices to the environmental elements, increasing costs, reducing operational life and providing an otherwise aesthetic unpleasing design.
There is desired an improved solid state light source generating a homogenous light beam having an improved cover design retarding environmental elements from penetrating about a lens to the light source electronics.
The present invention achieves technical advantages as a solid state light source having a unitary cover including an integral lens portion particularly useful in traffic control signals.
The solid state light apparatus comprises a housing having a cavity, an area array of light emitting diodes (LEDs) disposed in the housing cavity and generating a light beam, and a unitary transparent cover coupled to the housing and sealingly disposed across the cavity. This transparent cover has an integral inner portion and outer portion, whereby the inner portion is convex and shaped as a lens. The lens transmits the light beam emitted by the LED area array, with the outer portion extending outwardly from the lens. Since the lens is integral to the cover, there is no discontinuity between the inner portion and an outer portion which could otherwise allow environmental elements and water to permeate through the cover, which is a problem with many conventional traffic lamps currently being used.
In a preferred embodiment to the present invention, a light diffuser is disposed between the LED array and the lens. Since the unitary cover is transparent, the solid state light apparatus may further be equipped with an electronic detection device in the housing cavity and being viewable through the transparent cover second portion. This electronic device may include a camera, other electronic devices including video loop detectors, emergency detection devices and so forth. The unitary cover may be comprised of a plastic or glass material, but is preferably comprised of a lighter weight plastic material which can be formed by a molding process. The generated light beam preferably has an intensity complying with DOT requirements.
In a preferred embodiment, each LED comprises a semiconductor die such as a vertical cavity surface emitting laser (VCSEL) which generates a light source being generally perpendicular to the respective LED die, and may have an intensity of at least 100 mW. The lens is preferably a Fresnel lens. A method of using the traffic apparatus is also included within the scope of the present invention.